A report by progressive think tank The Australia Institute (TAI) has assessed the value of groundwater granted to coal mining companies in Queensland, based on New South Wales prices.

"On average per year the Galilee Basin mines will dewater around 50,000 megalitres per year," the Institute's Director of Research Rod Campbell said.

Mr Campbell said there was no charge for the use of groundwater in Queensland, which represented a taxpayer subsidy for industry.

"At a value of about $2,000 a megalitre, that amounts to about $100 million over the life of the region's mines.

"That's the sort of assistance that's not offered to mining or any other industry in New South Wales or other parts of Australia.

"At a time when governments are falling over themselves to declare, for example, the Carmichael mine as 'critical infrastructure', it's time to remember these projects are already being given a massive leg up at the expense of the environment and the taxpayer."

Mr Campbell said the report used water use figures from mining company estimates.

"The Carmichael mine itself says it expects to dewater around 3,944 megalitres per year through the life of the mine, meaning a subsidy of around $8 million," he said.

Mining industry hits back

The Queensland Resources Council (QRC) has described the report as "nonsense maths".

A spokesman said the figures were based on an inflated price, assuming all nine proposed Galilee Basin mines were in full production and using the most water possible.

"These are the worst case scenarios that assume the absolute largest volume of groundwater flows into pits that have not yet been approved or dug," he said.

The QRC spokesman argued that, based on TAI's report, Queensland's irrigation industry used about $1 billion worth of groundwater each year, with no charge.

He said another 30 per cent was used for rural purposes, adding up to an extra $300 million.

"Why aren't TAI getting upset about this $1.3 billion a year in 'subsidised water' for agriculture?" he asked.

"That's 13 times as much value of water they claim the Galilee mines will need."

The QRC said the groundwater that runs into coal mines was generally low in value due to poor quality and high salt levels which makes it inappropriate for other water users.

It said the Carmichael project would be the largest driver of new jobs in regional Queensland.